Screening for diseases is a process whereby a person who is not known to have one or more possible diseases undergoes a test to determine whether or not the person has any such diseases. Screening is often conducted on a large population, and therefore is likely to be inexpensive and minimally-invasive. Surveillance of a patient with a particular disease is a test that is conducted on a person with the disease to determine the severity of such disease, e.g., a degree of dysplasia in a patient with a known pre-cancerous condition. Effective screening and surveillance for the disease (e.g., dysplasia, cancer, etc.) of epithelial luminal organs systems, such as that of the gastrointestinal tract, urinary tract, pancreatobiliary system, gynecologic tract, oropharynx, pulmonary system, etc. utilize a comprehensive evaluation of a substantial portion of the mucosa. Certain beam scanning optical techniques, including time-domain optical coherence tomography (“OCT”), spectral-domain optical coherence tomography (“SD-OCT”), optical frequency domain imaging (“OFDI”), Raman spectroscopy, reflectance spectroscopy, confocal microscopy, light-scattering spectroscopy, etc. techniques have been demonstrated to provide critical information usable for diagnosis of a mucosal disease, including dysplasia and early cancer. However, these techniques are considered point-scanning methods, which are generally capable of obtaining image data only at one location at a time. In order to comprehensively screen large luminal organs, a focused beam can be rapidly scanned across the organ area of interest, e.g., over a large area, while optical measurements are obtained. Catheters, probes, and devices capable of performing this beam scanning function, are therefore generally used for an appropriate application of these and other optical technologies for screening large mucosal areas.
The screening described above should also be inexpensive so as to permit testing of a large population. In order to reduce the cost of screening, it may be preferable to provide a device or systems that is capable of being operated in a stand-alone imaging mode. Such stand-alone imaging can be conducted in unsedated patients, which significantly lowers the cost of the procedure and the complication rate relative to videoendoscopy. For surveillance, the comprehensive imaging procedure can be utilized to direct biopsies to the locations that contain the most severe disease. Since both the imaging and the intervention may occur during the same imaging session, the comprehensive imaging and interpretation of large volumetric data sets should be accomplished in a short amount of time.
Certain challenges exist when using scanned, focused light to comprehensively image luminal organs. Focused spots generally remain in focus for a certain range of distances from the probe to the tissue surface. For certain organ imaging systems, this focal distance (e.g., one metric of which is the Rayleigh range) is significantly smaller than the diameter of the luminal organ. As a result, screening the luminal organ mucosae typically is done by centering the distal/focusing optics of the imaging probe within the organ lumen so that the beam remains in focus throughout the comprehensive scan. Conventional systems employing a centering balloon have been described for OCT imaging of the esophagus. (See G. Tearney, “Improving Screening and Surveillance in Barrett's Patients,” NIH Grant No. R01-CA103769; and Boppart et al., “Optical Coherence Tomography: Advanced Technology for the Endoscopic Imaging of Barrett's Esophagus,” Endoscopy 2000; 32 (12), pp. 921-930).
Prior clinical studies are known to have acquired images likely only from discrete esophageal locations. The use of such conventional devices used an endoscopic guidance arrangement to identify regions of interest along the esophageal wall, and to direct the imaging probe to these locations. Certain components of the arrangement to provide high-resolution scanning of the focused beam should be considered. For each organ system, a certain catheter/probe types and modes of entry into the patient may be desirable for a less invasive operation. Different centering mechanisms are possible and designs are specific to the anatomy. The beam scanning probe optics should be positioned to the area of interest prior to conducting the imaging without an expensive or complex intervention. The beam focusing mechanism should contain an arrangement for correcting for aberrations caused by the probe sheath/centering mechanisms. In order to obtain accurate large area two- and three-dimensional images of the organ, the position of the beam should be known with precision for each data acquisition point.
Accordingly, there is a need to overcome the deficiencies described herein above.